Certain types of industrial printers can be applied to precision manufacture, for example, to the fabrication of electronic devices.
To take one non-limiting example, ink jet printers can be used to deposit one or more super-thin layers of an electronic display device or a solar panel device. The “ink” in this case differs from conventional notions of ink as a dye of a desired color, and instead can be an organic monomer deposited as discrete droplets that spread somewhat and meld together, but that are not absorbed and instead retain a deliberate layer thickness that helps impart structural, electromagnetic or optical properties to the finished device; the ink is also typically deliberately made to be translucent with a resultant layer being used to generate and/or transmit light. A continuous coat of the ink deposited by the printing is then processed in place (e.g., cured using ultraviolet light, or otherwise baked or dried) to form a permanent layer having a very tightly regulated thickness, e.g., 1-10 microns, depending on application. These types of processes can be used to deposit hole injection layers (“HILs”) of OLED pixels, hole transfer layers (“HTLs”), hole transport layers (“HTLs”), emissive or light emitting layers (“EMLs”), electron transport layers (“ETLs”), electron injecting layers (“EILs”), various conductors such as an anode or cathode layer, hole blocking layers, electron blocking layers, polarizers, barrier layers, primers, encapsulation layers and other types of layers. The referenced materials, processes and layers are exemplary only. In one application, the ink can be deposited to create a layer in each of many individual electronic components or structures, for example, within individual microscopic fluidic reservoirs (e.g., within “wells”) to form individual display pixels or photovoltaic cell layers; in another application, the ink can be deposited to have macroscopic dimensions, for example, to form one or more encapsulation layers cover many such structures (e.g., spanning a display screen area having millions of pixels).
The required precision can be very fine; for example, a manufacturer's specification for fabricating a thin layer of an organic light emitting diode (“OLED”) pixel might specify aggregate fluid deposition within a pixel well to a resolution of a picoliter (or to even a greater level of precision). Even slight local variations in the volume of deposited fluid from specification can give rise to problems. For example, variation in ink volume from structure-to-structure (e.g., pixel-to-pixel) can give rise to differences in hue or intensity differences or other performance discrepancies which are noticeable to the human eye; in an encapsulation or other “macroscopic” layers, such variation can compromise layer function (e.g., the layer may not reliably seal sensitive electronic components relative to unwanted particulate, oxygen or moisture), or it can otherwise give rise to observable discrepancies. As devices become smaller and smaller these problems become much more significant. When it is considered that a typical application can feature printers having tens-of-thousands of nozzles that deposit discrete droplets each having a volume of 1-30 picoliters (“pL”), and that manufacturing process corners for the printheads can lead to inoperative nozzles and individual error in any of droplet size, nozzle location, droplet velocity or droplet landing position, thereby giving rise to localized ink volume delivery variation, it should be appreciated that there are very great challenges in producing thin, homogeneous layers that closely track desired manufacturing specifications.
One source of error in achieving fine precision relates to the use of mechanical components in the fabrication processes relative to the scale of products being manufactured. As a non-limiting example, most printers have mechanical conveyance systems that move one or more printheads, a substrate, or both in order to perform printing. Some printers also feature conveyance systems for rotating or offsetting components (e.g., moving or rotating printheads to change effective pitch between nozzles); each of these conveyance systems can impart fine mechanical or positioning error that in turn can lead to non-uniformity. For example, even though these conveyance systems typically rely on high-precision parts (e.g., precision tracks or edge guides), they can still impart jitter or translational or rotational inaccuracy (e.g., such as millimeter, micron or smaller scale excursions in the transport path) that makes it difficult to achieve the required precision and uniformity throughout the transport path lengths used for manufacture. To provide context, an apparatus used to fabricate large size HDTV screens might feature a “room sized” printer which is controlled so as to deposit an ultra-thin material layer on substrates meters wide by meters long, with individual droplet delivery planned to nanometer-scale coordinates; the transport paths in such an apparatus can be meters in length. Note that there are many other mechanical components that can give rise to some form of error in such a system, for example, transport path systems used to interchange printheads, camera assemblies to align or inspect a substrate, and other types of moving parts. In such a system, even very fine precision mechanical parts can create excursions that affect the nanometer-scale coordinates just referenced. Thus, the required layers become thinner and thinner, and the require precision becomes smaller and smaller relative to the product being fabricated, it becomes even more imperative to carefully control and/or mitigate sources of potential positional error.
There exist some conventional techniques for reducing positional and translational error generally in these types of fabrication systems. First, a substrate can be coarsely-aligned with printer transport and then manually fine-aligned (potentially repeatedly during the fabrication process); such a process is time-consuming, i.e., it generally impedes the goal of having an automated, fast, assembly-line style process for producing consumer products. It is also generally quite difficult to obtain the required micron- or nanometer-precision with such a manual process. There also are some errors that cannot be adequately addressed with such a technique, for example, errors caused by transport path discrepancies, as just introduced above (e.g., error which manifests itself after a substrate has been aligned). As a second example, US Patent Publication No. 20150298153 relates to processes that measure fine positional and/or rotational errors in substrate position and that correct for those errors in software, for example, by reassigning which nozzles are used to print or by otherwise changing the nozzle drive waveforms which are used to fire nozzles; in other words, generally speaking, these techniques attempt to “live with” fine positional and rotational error (thereby preserving print speed) and they then attempt to adjust which nozzles are used and when and how those nozzles are electronically controlled, so as to remedy error (e.g., using a preplanned raster without having to re-adjust scan paths dependent on error). However, despite the utility of compensating for alignment error in software, the measuring and accounting for this error and re-computing firing assignments for thousands of nozzles in software can take substantial computing resources and time.
What are needed are additional techniques for correcting for motion, rotation and position error in mechanical systems in a manufacturing apparatus. Still further, what are needed are techniques for correcting for error in a moving component of a manufacturing system in order to simulate an “ideal” edge or transport path. Such techniques, if applied to precision manufacturing processes, especially printing systems of the type described, would reduce the need for substantial computing resources and time to re-render raster control data and, overall, lead to a simpler and/or faster and/or more accurate print process. The present invention addresses these needs and provides further, related advantages.
The subject matter defined by the enumerated claims may be better understood by referring to the following detailed description, which should be read in conjunction with the accompanying drawings. This description of one or more particular embodiments, set out below to enable one to build and use various implementations of the technology set forth by the claims, is not intended to limit the enumerated claims, but to exemplify their application. Without limiting the foregoing, this disclosure provides several different examples of techniques for mitigating transport path error in a manufacturing apparatus or printer, and/or for fabricating a thin film for one or more products of a substrate as part of a repeatable print process. The various techniques can be embodied in various forms, for example, in the form of a printer or manufacturing apparatus, or a component thereof, in the form of control data (e.g., precomputed correction data or transducer control data), or in the form of an electronic or other device fabricated as a result of these techniques (e.g., having one or more layers produced according to the described techniques). While specific examples are presented, the principles described herein may also be applied to other methods, devices and systems as well.